The present invention relates to a remote identification device. It can be applied notably to the identification of objects such as vehicles for example, the identification being done in a interrogation-and-response process by means of radar signals between an interrogation transmitter and an object to be identified, the identification requiring no energy source on the part of the object to be identified, the transmitter and this object to be identified being possibly separated by a long distance of the order of several hundreds of meters for example.
The identification of vehicles notably is generally done by sight and therefore requires human activity. This identification is therefore highly dependent on the eyesight of the person making the identification, the cleanness of the identification plate of the vehicle and local visibility in particular. Photographic methods may replace human intervention but then the latter two constraints still remain.
At short distances, there are many types of equipment capable of automatically and reliably identifying an object provided with a passive responder. An example that may be cited is that of certain anti-theft systems with which big dispensing machines in particular are equipped. These systems interact remotely with a diode. However, the interaction distance of these systems is only a few meters because, beyond a certain distance, the energy received by the diode is too small to create a voltage that exceeds its threshold voltage. It would be possible, for example, to increase the distance of the radar that sends the interrogation signal to increase the range of the systems using passive responders. However, these systems would then no longer be compatible with a short-range operation for there is the risk that the responder might be destroyed by the power received, notably at its detection diode.
For long distances, automatic identification systems based on interrogation and response always require an energy source proper to and associated with the responder.